Apparatus for conducting solid-fluid reactions



June 6, 1961 J. E. CARTER El'AL 2,987,381

APPARATUS FOR CONDUCTING SOLID-FLUID REACTIONS 2 Sheets-Sheet 1 FiledApril 10, 1958 INVENTORS Jaw/=0 few/N (a/W55 67/19/1 15: 6391/656000/7/04 HTTOE/VEY June 6, 1961 J. E. CARTER El'AL 2,987,381

APPARATUS FOR CONDUCTING soummzm REACTIONS 2 Sheets-Sheet 2 Filed April10, 1958 1 m u w United States Patent 2,987,381 APPARATUS FOR CONDUCTINGSOLID-FLUID REACTIONS Joseph E. Carter and Charles B. Goodrich,Huntington,

W. Va., assignors to The International Nickel Company, Inc., New York,N.Y., a corporation of Delaware Filed Apr. 10, 1958, Ser. No. 727,592 3Claims. (Cl. 23-284) The present invention relates to an improvedapparatus and method for conducting reactions between solids and fluidsand, more particularly, to an improved apparatus and method forconducting reactions between gases and finely-divided solids.

The first problem in all reactions between fluids, e.g., gases, andfinely-divided solids is to secure contact between the fluid and thesolid. In the case of lump or granular materials it is easy to obtaincirculation of gases through porous beds of the solid and secure goodcontact between the gas and the surface of each large particle. However,the ratio between surface area and weight of large solid particles islow and the penetration of the gas to the center of the particle isusually very slow. The use of finely-divided solids provides a muchgreater surface area per unit of weight and a lesser distance from thesurface to the center of the particle, thus greatly speeding the rate ofreaction. The use of finely-divided solids poses other problems,however, for it now becomes impossible to obtain good gas circulationthrough a static bed and any disturbance of the bed immediately createsa dust problem.

Another requirement of most gas-solid reactions is control oftemperature throughout the reacting bed. This can be most diflicult instatic beds, or very precise under conditions of rapid solid movement.Again, however, turbulence combined with gas flow through finely-dividedsolid beds creates problems of dust recovery which often negate otheradvantages of using finely-divided solids.

Various methods of reacting gases with finely-divided solids have beendevised with the view of increasing reaction rates and yields by seemingbetter gas-solid contact and better temperature control. These includehand or mechanically rabbled reactors, multiple hearth fur- 1 aces,flash roasting furnaces, rotary kilns and fluid bed reactors. The rotarykiln has been successfully used for a wide variety of gas-solidreactions and the more recent fluid bed techniques achieve excellentresults where finelydivided solids can be maintained in a fluidcondition. All of these methods are subject to dusting problems however,and often the equipment required for dust collecting and returning thedust to the reactor is more complicated and expensive than the reactoritself. Furthermore, any dust collecting system which must return dustto the reactor is inefiicient and mechanically troublesome. Reactantleaving the reaction chamber is no longer in the zone of optimumtemperature. In some reactions, for example, gas synthesis, the wrongproducts are thus formed and actually become impurities.

Although many attempts were made to overcome the foregoing difficultiesand other disadvantages, none, as far as we are aware, was entirelysuccessful when caried into practice commercially on an industrialscale.

We have now discovered apparatus for reacting fluids with solids and,more particularly, of reacting gases with finely-divided solids whereina good contact of gas to solid is achieved and wherein satisfactorytemperature control of the reaction is likewise achieved but wherein thedusting problem which has plagued prior art methods is eliminated. Theapparatus contemplated by the present invention provides a solid incontact with a fluid at all times and thus maintains the solid in thezone of reaction and under optimum control.

2,987,381 Patented June 6, 1961 It is an object of the present inventionto provide an improved apparatus for reacting fluids and solids whereinthe dusting problem associated with reactions involving finely-dividedsolids is eliminated.

Another object of the invention is to provide an improved apparatus forcarrying out reactions between fluids and solids and, in particular,between finely-divided solids and gases.

The invention also contemplates providing an apparatus for reactingfluids and finely-divided solids wherein good fluid-solid contact andgood temperature control is achieved.

It is a further object of the, invention to provide an apparatus forreacting solids wherein positive control of dusting from the solids isachieved.

The invention further contemplates providing an improved apparatus forcarrying out reactions between gases and finely-divided solids whereinloss of dust from the apparatus is prevented.

Other objects and advantages will become apparent from the followingdescription taken in conjunction with the accompanying drawing, inwhich:

FIGURE 1 depicts a rotary kiln constructed in accordance with theinvention for carrying out reactions between a gas and a finely-dividedsolid;

FIG. 2 depicts schematically an apparatus for carrying out the reactionsbetween finely-divided nickel and carbon monoxide under conditions ofelevated temperature and pressure to produce nickel carbonyl; and

FIG. 3 shows the cross section of a kiln constructed in accordance withthe invention which is provided with high pressure jets to remove fromthe sides of the kiln an adhering layer of solids.

Broadly stated, the present invention is directed to an apparatus whichcomprises the combination of a rotary kiln adapted to contain afinely-divided solid and having at least a portion of the surfacethereof made of a filter material which is permeable to fluids but isimpermeable to finely-divided solids, and a fluid-impermeable enclosuresubstantially surrounding said kiln and adapted to provide a free spacebetween the outer surface of said rotary kiln and the inner surface ofsaid enclosure, means for introducing a fluid to the interior of saidrotary kiln, means for conducting a fluid from said enclosure, means forintroducing finely-divided solid material to the interior of said rotarykiln, and means for rotating said rotary kiln. The apparatuscontemplated in accordance with the invention is particularly adaptablefor conducting reactions between a fluid, e.g., a gas, and afinely-divided solid to produce a fluid product.

In accordance with the invention, the finely-divided solid is confinedin a reaction zone in the form of the chamber of a rotary kiln having atleast a portion of the wall thereof constructed of a filter material.Such filter materials are well known in the art and may comprise aporous non-metallic material, such as a ceramic, or a porous metallicmaterial, such as porous stainless steel, porous nickel-copper alloy,porous nickel-chromium-iron alloy, porous high temperature alloysincluding age-hardenable alloys, porous metal-ceramic alloys, aluminum,etc. Such metallic filter materials are advantageous in that they arecharacterized by substantial mechanical strength. -Such filters may havea variety of pore sizes but in general the filters employed inaccordance with the present invention will have a maximum mean pore sizeofv about microns. Filters having finer mean pore sizes as fine as about5 microns and even finer may be employed depending upon the nature ofthe reaction involved, the particle size of the solid material treated,and the efiiciency of filtration desired. The particle size of the solidmaterial treated in accordance with the invention may be within theusual range of particle sizes which are employed in conducting fluid bedreactions, i.e., about 10 to 400 mesh (0.0787 inch to 0.0015 inch). Thein: vention is not limited to solids having the foregoing particle sizesince a mechanical means of agitation embodying a rotary kiln isemployed in accordance with the invention. Accordingly, the particlesize of the finely-' divided solids treated in accordance with theinvention may lie between sub-micron sizes and /2 inch particles,

or even coarser.

Preferably, the apparatus contemplated in accordance with the inventioncomprises an inner chamber or container comprising a rotary kiln havingporous walls and an outer chamber or container made of impermeablematerial defining a space between the outer wall of the inner chamberand the inner wall of the outer chamber. A complete circuit for thereactant fluid and the fluid products of reaction is provided in thatthe reactant fluid, e.g., gas, is introduced into the interior of therotary 4 I F. to 1000 F. or even higher) is introduced through the inletpipe 9 from whence it passes through the internal filter 10 and thecheck valve 12 into the kiln. The kiln is rotated by the drive 15applied to the shaft 3. The hot hydrogen heats and reduces the nickeloxide charge in the kiln and the gaseous products of reaction passthrough the porous cylindrical portion of the kilnl into thesubstantially annular intermediate space 1A and are then led through theport 16 of the outer pressure vessel.

kiln and is caused to travel through at least a portion of thefinely-divided solid contained therein, thence through the porous wallsof the rotary kiln and through the space between the inner and outerchambers to exit ports in the outer chamber. Positive flow of the fluidreactant and of the fluid products of reaction is thus achieved. Theinner and outer chambers are preferably constructed to permit carryingout reactions at elevated temperatures and pressures. If need be,auxiliary heating and/ or cooling means may be provided to securetemperature control Within the kiln and the outer walls of the outerchamber may be insulated where required. The movement of fluid reactant,e.g., gas, through the rotary kiln by itself causes further agitation,e.g., turbulence or movement, of the solid particles contained thereinand this move: ment is. enhanced by rotation of the inner chamber orrotary kiln. The dust created by the agitation is stopped by the porouswalls of the inner chamber or rotary kiln and is retained therein sothat the solids continue to react The flow of hydrogen is regulated tohold at least the finer portion of the charge on the porous surface ofthe kiln as this provides excellent gas-solid contact. In the case ofthe reduction of nickel oxide with hydrogen, it is convenient todecrease the gas fiow when the reduction nears completion in order tokeep the porous kiln surface relatively clean and to keep a largerportion of the charge tumbling in the bottom of the kiln. In thismanner, sintering of the fine reduced material to the side of the kilnis prevented.

It will be appreciated that the finer portion of the charge is held incontact with the surface of the porous kiln 1. When the build-up of finematerial on the porous surface of the kiln becomes too thick, anexcessive pressure drop in the hydrogen line may result. In order tocorrect this condition, the gas flow may be reversed momentarily andthis will drop the charge from the kiln surface and free the poresthereof. When the gas flow is reversed, the check valve 12; closes andthe gas flow must then pass through the internal filter 10, thus keepingthe charge in the kiln.

Example 11 The production of nickel carbonyl by reacting carbon monoxidewith finely-divided nickel will now be discussed with the gas passingthrough said kiln and the walls v thereof.

In order to give those skilled in the art a better under: standing ofthe invention, the following illustrative examples are given:

' Example I in conjunction with FIG. 2 which is a simplified flow sheetfor carrying out the aforementioned reaction in accordance with theinvention. Finely-divided nickel having a particle size of'below about100 microns is 0 charged 'into the cylindrical rotary kiln 1 which isconably is cylindrical in form and has at least a portion or V thesurface thereof made of a porous material such as porous stainless steelsheet. Kiln 1 is enclosed in a sub stantially cylindrical stationarypressure vessel 2 to allow operation under pressure, to providetemperature control andto control flow of exit gas coming from the kiln.The kiln 1 is provided with a hollow driving shaft 3 which is journaledin bearings 4 and is provided V a packing gland assembly 5, sealingrings 6 and cooling water supply pipe 17. .A removable cap 7 which isprovided with water connections .8 and an inlet gas pipe 9 permitsloading of the kiln. The kiln is also provided with an internal filter10 whichis screwed into the neck 11 of the kiln and which isconveniently made from the same filter material employed in rotarykiln 1. A check valve 12 is provided at the end of the internal filter10. a A bearing 13 provided with a water jacket '14 completes theassembly of the unit. The kiln is adapted to be turned to an uprightposition such that the cap 7 ison top. While in this position, the capand internal filter are removed and a'charge of nickel oxide having aparticle size of /2 in'ch'to 8 mesh (0.0937 inch) including as much 7 as5% fines below. 8 mesh is introduced into the The internalfilter and capare replaced and the piping reconnected. The kiln is then rotated to ahorizontal posi- 7 structed of porous stainless steel having a mean poresize of about 20 microns. The rotary kiln 1 is rotated by an externaldrive mechanism through a shaft 3 which is journaled in bearings 4. Therotary kiln 1 is enclosed in a stationary shell 2 which is provided witha seal 21 to prevent leakage of gases at the operating pressure. Acompressor 22: compresses carbon monoxide to the operating pressure ofabout 28 atmospheres (although the pressure may be much higher or lower,e.g., about one atmosphere to about atmospheres) and the compressedcarbon monoxide is introduced into the kiln 1 through inlet 23. Most ofthis gas enters through the check valve 12 though it is also free toflow through the porous internal metal filter 10 positioned within therotary kiln 1. In operation, the charge of nickel powder is exposed tothe streamof carbon monoxide due to the tumbling action through therotation of kiln 1 by means of the'shaft 3 which is powered by the drive15. The finer particles of the metal powder adhere to the'fporous metalwalls of the kiln 1 and distributeithemselves over the surface in auniform layer due to the pressure of the gas flowing through the porouswalls of the This action provides excellent gas-solid contact at thekiln wall. The layer of solids held against the kiln wall can be removedand replaced with a fresh layerof solids from the charge by a periodicbrief reversal of carbon monoxide gas flow. The carbon monoxide notconsumed by the reaction and the nickel carbonyl formed by' the reactionpass through the porous walls of the kiln 1 and leave the outer vessel 2at the exit port 16. These gases, which are heated in the range of aboutl00 to about 500 F. by the reaction, are led through the condenser 27where they are cooled to condensenickel carbonyl .asa liquid which iscollected in the tank 28. "Ihe unused carbon monoxide the production ofnickel carbonyl is an exothermic reaction, an optional blower 30 isprovided in the event it is necessary to circulate additional coolcarbon monoxide through the outer vessel 2 in order to cool the walls ofthe kiln 1. This gas is admitted through the ports 31 in the outer shell2 and may be employed to control the temperature of the reaction. Whenthe thickness of the layer of solids on the porous walls of the kiln 1is built up to an undesirable extent, the reactant gas flow is reversedin order to backblow gas through the porous metal wall so as to providea control of the thickness of the solids layer. This is accomplished byoperating the four-way valve 32 which reverses the direction of gasflowthrough the kiln. The by-pass line 33 contains check valve 34 and anorifice 35 which allows about onehalf the volume of gas to by-pass thekiln. The balance of the gas passes through the porous walls of the 1,removing solids adhering to the inner surface. Check valve 12 closes,thus forcing the gas to leave the kiln through the porous inner metalfilter 10, thereby insuring that no dust escapes from the kiln.

In carrying out the reaction as depicted in accordance with the flowsheet in FIG. 2, frequent removal and replacement of the layer of finesadhering to the porous walls of the kiln 1 is an important factor inobtaining a rapid extraction of nickel in the form of nickel carbonyl. Atechnique for accomplishing this purpose is continuous backblowing by asource of reactant fluid, e.g., gas, which is achieved by directing aline of high pressure gas jets against the porous outer surface of thekiln, 1. This method is illustrated in FIG. 3 showing the continuousremoval of the adhering layer of fines 36 just before said layer isimmersed in the tumbling bed of solids 37 at the bottom of the kiln. Asshown in this cross sectional view, the layer of adhering solids isremoved by the high pressure gas jets 38 positioned at a point shortlybefore the rotating side of the kiln 1 is submerged below the bed ofsolids 37 and a new layer is formed at the point 39 on the rotating sideof the kiln 1 as the side emerges above the bed of solids 37. In thismanner, a continuous sweeping of the porous metal face of the kiln isprovided. It will be noted that the aforementioned line of high pressuregas jets is placed substantially parallel to the major axis of thecylindrical rotary kiln.

Example III In still another example demonstrating the versatility ofthe apparatus contemplated in accordance with the present invention, thecharge of nickel oxide sinter reduced by the procedure described inExample I is treated further to produce nickel carbonyl without removingit from the kiln. This is accomplished by cooling the charge of reducedsinter in the to about 100 F. and passing carbon monoxide at atemperature of about 80 F. and a pressure of about 30 atmospheresthrough the kiln until the nickel metal content of the charge issubstantially extracted and recovered as nickel carbonyl in the mannerdescribed hereinbefore in connection with FIG. 2. In this manner, thenickel content of the original nickel oxide charge is substantiallycompletely recovered as nickel carbonyl without removal of the originalnickel oxide charge or of the reduced nickel from the apparatus.

The present invention also contemplates conducting reactions betweenfinely-divided solids and fluids to produce a fluid product wherein thefinely-divided solid is confined in a reaction zone bounded by a filteror porous membrane and is agitated in contact with the fluid while insaid reaction zone and wherein the fluid product of reaction iswithdrawn from the reaction zone through said filter or porous membranewhich is permeable to the fluid reaction product and the fluid, e.g.,gas, but is impermeable to the finely-divided solid.

Those skilled in the art will appreciate from the foregoing descriptionthat the apparatus contemplated in accordance with the present inventionare particularly applicable to reactions between a solid and a fluid toproduce a fluid product and including for example, the reaction betweencarbon monoxide and nickel to produce nickel carbonyl and the reductionof nickel oxide with a gas such as hydrogen to produce water vapor. Theroasting of metal sulfides, such as nickel sulfide, with an oxidizinggas, such as air, may also be mentioned. In conducting such reactions,the filter material employed in the rotary wall and in the internalfilter mentioned hereinbefore (if one be used) are selected so as to bepermeable to the reactant gas and the fluid product of reaction butimpermeable to the finely-divided solid. The apparatus contemplated inaccordance with the invention is also applicable to processes whereinthe fluid, e.g., gas, which is conducted through the rotary kiln doesnot enter into the reaction involved, as in the case of the drying ofvarious sol-ids by passing relatively dry gas thereover at an elevatedtemperature to remove the water content of the solid as vapor, and toreactions involving decomposition of solid materials by heat, as in thecalcination of carbonates.

It will be apparent from the foregoing description that the outerchamber shown as reference numeral 2 in the drawing may be made of theusual structural metals, such as carbon steel, alloy steel, stainlesssteel, high-nickel alloys, etc., having regard-for the particularoperating conditions of temperature and pressure involved.

It will be appreciated that the apparatus of the present invention maybe applied to the reduction of the oxides of such metals as copper,nickel, iron, cobalt, manganese, etc., and to the formation of carbonylsof such metals as iron, nickel, cobalt, molybdenum, chromium, and theprecious metals. It will also be appreciated that conventionalatmospheres employed for reducing metal oxides may be introduced intothe apparatus and used in the process embodying the present invention.Thus, atmospheres such as water gas, producer gas, partly combustednatural gas, natural gas, cracked ammonia, etc., may be employed inconjunction with the present invention. The invention is applicable toreactions which take place over a wide range of temperature andpressure. Thus, when the invention is applied to the reduction of metaloxides, conditions in the rotary kiln may be controlled to providetemperatures in the range of about 300 F. to 2000 F. and pressures inthe range of about atmospheric to about 75 atmospheres. Again, inconjunction with the formation of metal carbonyls, pressures rangingfrom atmospheric to about 400 atmospheres and temperatures ranging fromabout F. to about 700 F. may be employed.

It will also be appreciated that the invention can be applied to theformation of metal carbonyl from a variety of materials containing metalvalues as low as about 1%, although preferably the metal value should beat least about 10% of the material treated. Thus, ores, concentrates andvarious materials such as grinding dust can be treated directly in theapparatus contemplated in accordance with the present invention toextract the metal value thereof as metal carbonyl even though the metalvalue be bound chemically in the material in the form of oxides, etc.

It will be noted that a number of advantages are provided in accordancewith the invention in carrying out reactions between finely-dividedsolids and fluids, e.g., gases, in employing the special rotary kilncontemplated in accordance with the invention. Thus, intimate fluidsolidcontact is achieved. It is possible to employ a high ratio of surfacearea to weight of the solid reactant. Good temperature control isachieved throughout the bed of solids. It is possible to operate atsubstantial pressure which results in an increase in the rate of manyreactions. There is no dust loss from the kiln vessel itself.Furthermore, positive control of reactant gas and fluid product isachieved and this is very important in the case where such materials areextremely poisonous, for

example, in the case where a reactant gas is carbon monoxide and 'afiuid product of reaction is nickel carbonyl. i

Although thcpresent inventipn has been described-in conjunction withpreferred embodiments, it is to be understood that modifications andvariations may be'resorted to without departing from the spirit andscope of the invention, as those skilledin the art'will readilyunderstand. Such modifications and variations are considered to bewithin the purview and scope of the invention and appended claims. fl ii i We claim: 7 7

1. An apparatus for producing nickel carbonyl from nickel powdena ndfiarbon monoxide under conditions of elevated temperature andpressure'comprising a substanf tially'cylindrical I Iary kiln having atleast a portion of the walls thereof made of porous metal having amaxirnuni means pore size of about 20 microns and being permeable tocarbon'monoxide' and nickel carbonyl but impermeable to nickel powder,anbuter metal chamber surroundingsaid rotary kiln and defining therewitha substantially annular zone, means for driving said rotary kiln, anauxiliary gas-conducting circuit for introducing carbon monoxide underpressure into the interior of said rotary kiln and for conducting nickelcarbonyl and unreact'ed carbon monoxide from said outer chamber, meansfor reversing gas flow in said circuit to provide a backblow 0.? ga n err su e a a ns the o t r u a of Said rotar k nd' a n e nal me al fi e andheck val e o at in s id. u t w hin a ta y to pre ent s sq a c of i k l,Po de rom S rotary kiln when the gas flow in said circuit is reversed.

2. An apparatus for conducting reactions involving finelyrdivided solidswhich comprises a substantially cylindrical rotary kiln having at leasta portion ofthe walls thereof made of a filter material from the groupconsisting of porous metallic material and porous non-metallic materialwhich has a maximum pore size of about 135 microns and is permeabletogas but'substantially impermeable to finely-divided solids, an outerchamber made of gas-impermeable materialsurrounding said kiln anddefining therewitha substantially annular zone,mc.ans for drivingsaidrotary kiln, auxiliaryineans comprising a gas-conducting circuit leadingto the interior of said rotary kiln and from the exterior of said outer.chamber, means for reversing the gas flow in said circuit, and aninternal filter and a check valve located within said rotary kiln toprevent discharge of finely-divided solids therefrom when the gas flowin said circuit is reversed.

3. An apparatus forreacting a 'gas with a finely-divided solid whichcomprises a substantially cylindrical rotary kiln having at least aportion of the wall thereof made of a porous filter material having amaximum mean pore size of about microns, an outer chamber made of agas-impermeable material surrounding said rotary kiln and definingtherewith a substantially annular zone, means for 'driving said rotarykiln, means for continuously introducing a'gas under pressure to theinterior of said rotary kiln, means for conducting gas from said outerchamber and a plurality of high-pressure gas jets placedsubstantially'parallel to the major axis of said rotary kiln anddirected against the porous outer surface of said rotary kiln at a pointwhere said surface, 'while in motion, is moving ina downward direction.

References Cited in the file of this patent UNITED STATES PATENTS635,574, McCabe Oct. 24, 1899 1,909,762 Grieb' May 16 1933 2,208,146Doyen July 16, 1940 2,334,555 Howard Nov. 16, 1943 2,473,993 Gresham etal. June 21, 1949 2,603,556 Miller July 15, 1952 2,750,260 Nelson et alJune 12, 1956 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTIONPatent N50 2,981,,381 I June 6 I961 Joseph Eo Carter e13 ale It ishereby certified that error appears in ;the above numbered patentrequiring correction and that the said Letters Patent should read ascorrected below.

Column 1 line 63 after "disoovered insert an 3 a column 7 line l8 for"means" read mean eelumn 8 line 1, after maximum insert mean Signed andsealed this 20th day of Marsh 19620 (SEAL) Attest:

ERNEST W. SWIDERV v DAVID L. LADD Attesting Officer Commissioner ofPatents

3. AN APPARATUS FOR REACTING A GAS WITH A FINELY-DIVIDED SOLID WHICHCOMPRISES A SUBSTANTIALLY CYLINDRICAL ROTARY KILN HAVING AT LEAST APORTION OF THE WALL THEREOF MADE OF A POROUS FILTER MATERIAL HAVING AMAXIMUM MEAN PORE SIZE OF ABOUT 135 MICRONS, AN OUTER CHAMBER MADE OF AGAS-IMPERMEABLE MATERIAL SURROUNDING SAID ROTARY KILN AND DEFININGTHEREWITH A SUBSTANTIALLY ANNULAR ZONE, MEANS FOR DRIVING SAID ROTARYKILN, MEANS FOR CONTINUOUSULY INTRO-